Increased competition drives development forward

The worldwide market of medium and high-speed four-stroke diesel engines is now as before distinguished by over-capacity and thus very competitive. Engine development is ? besides the typical requirements of higher power output, less fuel and lube oil consumption, improved reliability and longer service life ? also concentrating on cost reduction in the fields of manufacturing and service.

Against this background some companies presented at the 24th CIMAC World Congress in Kyoto, Japan, interesting engine developments in the field of medium and high-speed four-stroke marine diesel engines. This report deals with the latest developments of Hyundai, MAN B&W and Niigata.

Hyundai Heavy Industries

Since the introduction of the H21/32 engine series in 2001 by

Hyundai Heavy Industries

Company, two other engine series have been added to the so-called Himsen engine family. One is the H25/33 and the other the small H17/28 series. The prototype of the H25/33 series was originally jointly developed with Rolls-Royce Marine (Bergen Diesel).

To integrate this series into the Himsen family, it had to be largely redesigned. Thus there exists no longer any interchangeability with the prototype. The development of the H17/28 as the smallest engine series of the family is just underway and will be available on the market from the beginning of 2005, whereas the H 25/33 series already passed the classification approval in 2002.

The H17/28 series with a bore of 170 mm and a stroke of 280 mm will include 5-, 6-, 7- and 8-cylinder engines with an output per cylinder between 90 and 115 kW, depending on the engine speed, which will be standard 720 or 900rpm. Alternative maximum speeds with unchanged power output will be respectively 750 or 1000rpm. That means, the power range of this series will cover 450 to 920 kW. The expected specific fuel consumption will be in the order of 190 g/kWh.

The relatively long stroke ? Hyundai says it has the longest stroke of its class ? leads to a very low piston speed of only 6.7 respectively 8.4 m/s, but to a mean effective pressure between 23.6 and 24.1 bar. Marine diesel fuel or heavy fuel oil up to ISO 8217, RMK 55 may be used to run the engines.

The joint development of the 250 mm bore engine started with one prototype at each place, i.e. Bergen and Ulsan. Performance and reliability tests had been carried out at both places to confirm main parameters. The second prototype built by Hyundai already incorporated all design features adopted from the successful H21/32 series. After that, further developments at Rolls-Royce and Hyundai were pursued individually. Hyundai was mainly interested in increasing commonality among the engine types of the Himsen family to reduce manufacturing cost and improve serviceability.

The engine series H25/33 with a bore of 250 mm and a stroke of 330 mm is now on the market with six to nine cylinders, covering a power range between 1440 and 2700 kW at speeds between 720 and 900rpm. The corresponding piston speed is respectively 7,9 and 9,9 m/s and the BMEP goes up to 24.7 bar.

At the end of 2003 about 100 engines of the Himsen family had been delivered and 30 of them are in service.

MAN B&W Diesel

With the new L21/31 series ? bore 210 mm and stroke 310 mm ? MAN B&W is completing the medium-speed engine programme at the lower end. The engines are available with five to nine cylinders, covering the output range from 950 to 1935 kW at maximum speeds of 900 or 1000rpm. The five-cylinder engine is only available for generator drives. Piston speed reaches 9,3 to 10,3 m/s and the BMEP 24,0 to 24,8 bar. At 100 % MCR the engines have a specific fuel consumption of 184 g/kWh and at 85 % only 181 g/kWh. The lube oil consumption is 0,8 g/kWh.

Design goals were characterized by both genset application and main propulsion. A combination of design principles have been taken over from well proven large-bore engines especially from the 32/40 series.

Particular attention has been paid to standardising as many sub-assemblies as possible. To achieve the design task “pipe-less engine”, lube oil pump, cooling water pump, thermostats, filters etc. have been integrated into a “front end box”.

The result is a very compact design with maximum accessibility, including the attachments. To simplify engine installation at the shipyards all connections are arranged at the front end of the engine.

For the marine propulsion version, the arrangement of turbocharger and intercooler at the coupling end of the engine led to a short engine compared with similar engines of same output. To optimise part load operating conditions of fixed pitch propeller plants, these engines are equipped with a combination of waste-gate control and charge air by-passing facility. In the case of CPP plants the piping and valves of this arrangement can be avoided.

A design concept which improves maintenance conditions of engines up to a certain size is more and more used in conjunction with a new engine design: the cylinder unit comprising the complete cylinder head, the liner, valve train and connecting rod with piston. It was first introduced, ten years ago at SMM 94, with the new DEUTZ MWM 632 engine series (bore 250 mm, stroke 320 mm).

The MAN B&W 21/31 series is now also equipped with such a maintenance unit which can be exchanged within a very short time when servicing the engine. Overhaul may be carried out on board with the engine already back in operation.

Niigata Power Systems

At the beginning of the 1990s

Niigata Power Systems

Company introduced the V16FX high-speed engine (bore 165 mm, stroke 185 mm). To cope with the demands of high-speed vessels a new high-speed diesel engine series has been developed, the V20FX. The basic design concept had already been presented at the 23rd CIMAC congress in Hamburg. In the meantime , however, some important changes have been realised.

The V20FX series consists of 12-and 16-cylinder V-type engines with a bore of 205 mm and a stroke of 220 mm. The maximum continuous output is set to respectively 3000 and 4000 kW at a speed of 1650rpm. These values correspond to a maximum piston speed of 12.1 m/s and a mean effective pressure of 25 bar. With its mass of 13.5 tonnes, the 16-cylinder unit reaches a weight to power ratio of only 3.4 kg/kW.

Significant change

The most significant change of the engine concept concerns the turbo-charging system. In 2001 the engine was introduced with two large turbochargers. Due to customer specification, which asked for good acceleration and high output at low speed, a sequential turbo-charging system had been adopted. This system consists of two small master chargers, operating alone at low load, and two medium-size chargers as slaves, working under intermediate and high load conditions. As expected, the engine performance with four turbo-chargers was superior to the unit with only two large turbo-chargers.

In this connection the fuel injection system also had to be optimised. Special emphasis was placed on stable idle and low load performance.

Another important change has been carried out on the thin-walled cylinder liner. To improve the behaviour of the liner in addition to the standard supports at top and lower end, a third support at about half length of the liner had been arranged.

The Niigata V20FX high-speed diesel engine series is now optimised for low-load operations. Six engines in service now for about one year, have been operating without problems. Another 20 are on order. n